Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$198.44	6.855%	$212.0431	$212.04	$212.05	$212.00
Purchase #2	$241.57	6.599%	$257.5112	$257.51	$257.50	$257.50
Purchase #3	$178.54	3.665%	$185.0835	$185.08	$185.10	$185.10
Purchase #4	$167.33	13.671%	$190.2057	$190.21	$190.20	$190.20
Purchase #5	$225.56	13.254%	$255.4557	$255.46	$255.45	$255.50
Purchase #6	$98.82	12.481%	$111.1537	$111.15	$111.15	$111.20
Purchase #7	$62.83	3.108%	$64.7828	$64.78	$64.80	$64.80
7 purchase totals =	$1,173.09		$1,276.2357	$1,276.23	$1,276.25	$1,276.30